Gene regulation is a complex process that orchestrates the precise timing and location of both gene activation and gene silencing. Genomic imprinting is a specialized mechanism whereby a gene displays silencing of one parental allele. The imprinted region on human chromosome 11p15.5 and its homologous domain in the mouse consists of a cluster of genes that are silenced on the paternal chromosome by an antisense non-coding RNA, Kcnq1ot1. Very little is known of the molecular mechanisms involved in allele-specific silencing and the role of the non-coding RNAs in modulating this process. This proposal will first exploit transgenic RNA interference technology to test the role of Kcnq1ot1 in establishing imprinting at this locus. In the second and third aims, we will study the epigenetic processes that allow some genes to escape silencing, applying a combination of bioinformatic, biochemical and in vivo approaches to identify regulatory elements in this domain that interact physically and create transcriptionally active domains interspersed with the silenced regions. Identifying the molecular mechanisms underlying the establishment and maintenance of imprinting will advance our understanding of human growth defects and disease.